Propeller hub and associated blades



Feb. 8, 1949. J. H TS r 2,460,910

PROPELLER HUB AND ASSOCIATED BLADE 4 Sheets-Sheet 1 Original Filed Jan. 19, 1944 xii? Zhwentors J4cx MSHEETS mum E. Cos/IMAM (It orncg Feb. 8, 1949. J. H. SHEETS AL 2,460,910

PROPELLER HUB AND ASSOCIATED BLADE Original Filed ,Jan. 19, 1944 5 4 sheets-she t? I Summers JACK H.8uzsrs v MnumcsliCusnmau Cmomcg Feb. 8, 1949. H- SHEETS EI'AL 2,460,910

PROPELLER HUB AND ASSOCIATED BLADE Snnentors JA cx b. Suegrs MA ue/cz E. Cash/MN 4 Sheets-Sheet 3 Original Filed Jan. 19, 1944 (3 torneg Feb.- 8, 1949. I Y J, SHEETS HAL 2 ,460,910

PROPELLER HUB AND-ASSOCIATED BLADE 4 sheet -sheet 4 Original Filed Jag. 19, 1944 l ki li SID 286 Summer LOAD SIDE OF A SPL/NED TOOTH FIFTH 700T J CK '9. 5115578 A T PITCH o/AMETEK TO 65 neon THIS END Mame/c: [I (US/{NAN COMIC/DENT WITH LOAD SIDE 5' OF GEAR roar A7 P/rcH l i I DIAMETER WITH/N 0 attonc Patented Feb. 8, 1949 I 2,460,910 PROPELLER HUB AND ASSOCIATED BLADES Jack H. Sheets and Maurice E. Cushman, Verona, N. 3., assignors to Curtiss-Wright Corporation, a corporation of Delaware Uriginal application January 19, 1944, Serial No.

519,064. Divided and this application Novembe: 6, 1944, Serial No. 562,167

This invention relates to aircraft propellers and more particularly to such propellers wherein the blades thereof are associated with a controllable pitch change mechanism. M

More specifically, the invention resides in a structural improvement in the root or shank end portion of the blades of such propellers whereby an integral flange and a blade index-coupling means may be incorporated therewith.

This application is a division of our co-pending application Serial No. 519,064, filed January 19, 1944.

In some types of propeller assemblies, the shank end of each blade is journalled in the propeller hub by means comprising a plurality or stack of annular, anti-friction bearings of the one-piece ball race type, a flanged, screw-threaded retaining member and a threaded, locking ring or blade-retaining nut.

This construction requires that the outer diameti'al surface of the blade shank be uniform throughout for the passage thereover of. the said anti-friction bearings. In the assembly of the aforesaid elements, the locking nut is first passed over the shank of the bladefthen the stack of bearings, and finally the flanged retaining member or plug including a blade actuating gear segment, screw threaded into the root end of the blade and secured against movement as by means of a dowel pin.

The foregoing known construction has certain disadvantages in that it increases the weight of the blade assembly unnecessarily, entails more costly manufacturing operations such as thread cutting, for example, and does not provide a positive safety factor for the reason that should the flanged plug become disconnected from the blade, while in operation, the blade would be free to become detached from the propeller hub. Moreover, in regions where screw threads occur,

a severe stress concentration factor in such regions may cause fractures and failure of a particular part or parts in the propeller assembly.

The present invention not only obviates the above noted disadvantages but it also frees space within the root end portion of the blade, formerly occupied by the flanged retaining plug as herein'before noted, for the formation on the interior, and the reception within the blade shank, of a blade index-coupling means including the hub of a blade actuating gear segment. Accordingly, it is an object of the invention to provide a novel propeller blade assembly which is lighter in weight, provides a positive safety factor, requires a minimum of manufacturing opmethod of operation, together with additional ob- 5 Claims. (01.,170-16058) A further object of the invention is to provide a propeller assembly wherein each blade is adapted to be indexed for concise angularity whereby aerodynamic balance of all the blades is more readily achieved.

Another object of the invention is to provide a propeller blade with a novel shank end construction whereby a plurality of blade indexcoupling elements including a blade actuating gear segment may be associated therewith.

A further object of the invention is to provide a propeller blade with an improved shank end construction whereby an interlocking coupling may be made between the blade and a gear segment adapted for actuating said blade.

Another object of the invention is to provide a propeller blade, as specified, with an improved shank end construction which obviates the necessity for screw threads and what is more important, the prevention of severe stress concentration factors in the shank region of a blade whereby the likelihood of fractures and/or the failure of a part is materially decreased.

A further object of the invention isto provide a propeller blade joumalling means wherein the blade is held rigid yet sufficiently free to permit partial rotation about its axis, and which is also held secure against radial movement either inwardly or outwardly with respect to its hub socket.

With the above and other objects in view, the invention resides in the novel construction, combination, and arrangement of parts, the novel features of which are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its jects and advantages thereof, will be understood from the following description of a specific embodiment, when taken in connection with the accompanying drawings, in which:

Figure 1 is a fragmentary sectional view illustrating the manner in which the improved shank portion of a propeller blade is associated with the blade carrying hub;

Fig. 2 is a transverse sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is an exploded view in plan and partly in section and illustrating the manner in which the blade-retaining nut. and a .stack of split bearings are positioned on the shank portion of the improved propeller blade;

Fig. 4 is a fragmentary sectional on the line 4-4 of Fig. 1;

Fig. 5 is a fragmentary plan view illustrating a feature of the invention;

Fig. 6 is a reduced plan view of a flexible, ballretaining cage;

Fig. 7 is a sectional view taken on the line 1-1 of Fig. 6;

Fig. 8 is an elevational view of the root end of the blade shank illustrating the manner of assembling the flexible, ball-retaining cages there- Fig. 9 is an elevational view looking from the line 9-9 of Fig. 10 into the root end of the blade shank and illustrating the angular location of one of the reference marks, shown in Fig. 5, with respect to the chord line of the blade section indicated by the broken lines;

Fig. 10 is a sectional view of the blade shown in Fig. 9; and

view taken Fig. 11 is a top plan view of the gear segment per se illustrating the angular relation of the load side of a spline tooth with respect to the load side of the fifth tooth (counting from the right of the figure) of the gear segment.

Referring to the drawings and to Fig. 1 in particular, one of the blade-receiving sockets in of a multiple socket propeller hub II is shown with the improved shank portion [2 of a hollow blade l3 journalled therein.

In accordance with the invention, the improvements in the blade shank 12 comprise an external flange l4, integral with said shank at the root end thereof, whereby the threading of a bore within the shank portion l2 and the attachment thereto of a flanged screw plug is obviated, said improvements further comprising an inwardly extending flange provided with splines i5 located within the bore l6 and forming one element of an index-coupling means as and for the purpose hereinafter described.

The foregoing improvements, together with the blade index-coupling elements associated with the shank portion l2, will now be described.

The external flange M is suitably shouldered to provide a circular flanged seat engaged by an anti-friction bearing H which comprises inner and outer ball races Ila, and "b respectively. The hearing I! is retained on the blade shank flange [4 by a snap ring l8 which occupies an annular groove provided therefoNin said flange M as clearly shown in Fig. 1.

Disposed around the shank I 2 and seated on the flange I4 is an anti-friction main bearing 19 which, in the example shown in Figs. 1 and 3, comprises two accurately matched half-sections or raceway-forming members 20 and 2| with a plurality of spaced, annular raceways formed therein and constituting the inner race of the bearing IS. The aforesaid bearing 19 also comprises-a plurality of ball-retaining cages 22 for a plurality of anti-friction ball members 220., each of said cages, in the preferred example shown, being formed by two duplicate half sections.

However, in lieu of the said duplicate halfsections and as shown in Figs. 6, '7 and 8, there may be utilized flexible one-piece ball cages or retainers 22m formed of spring wire and in a manner adapted to present spaced, upstanding loops 2211, for retaining a plurality of similar ball members 220. The aforesaid flexible, one-piece ball cages 22m are positioned in the respective raceways of the inner race sections 20 and 2| much after the fashion of a bracelet with the respectivefree ends thereof substantially in abutting relation.

Referrlng further to Figs. 1 and 3,"a plurality ill, at the top thereof, is a blade-retaining ring or nut 23' which engages the uppermost raceway 22b to positively hold the aforesaid parts in assembled relation. A resilient U-shaped seal 24 is maintained in sealing relation with respect to the exterior surface of the shank l2 and the interior surface of the nut 23 by a pair of flexible garter rings 240:. A two-piece metal ring 25, having a short upstanding flange is positioned on top of and held in engagement with the U- shaped seal 24 by a flange 23a formed on the aforesaid nut 23. The split ring 25 serves to reinforce the resilient seal 24 to thereby prevent escape of a lubricant in response to centrifugal force generated during operation of the blade in a propeller assembly. As known in the art, lugs 23b utilizable for blade-balancing purposes together with a key 230 are secured to the upper face of the blade-retaining nut 23 by suitable screws, the lugs 23b and key 23c having short arcuate configuration.

In a known manner, the interior chamber defined by the blade I3 is sealed by a shell 2311 which, in suitable. manner, has a balance plug' 23c secured to its interior surface and projecting inwardly.

For a description of the index-coupling means, reference is to be had to Fig. 1 wherein the hub H is shown as enclosing the final gear 26 of a blade-actuating power unit generally indicated'at 27, said gear 26 being shown in mesh with a gear segment 28 provided with a shouldered hub 29 having a series of splines 30 about its upper reduced diametral portion.

The hub 29 of the aforesaid gear segment 28 is also provided, on its lowermost exterior surface, with an annular groove adapted for the reception of a suitable gasket 3| of synthetic rubher, for example, which, when the parts are assembled as shown, coacts with the adjacent surface of the bore It to form a lubricant seal as will be understood.

The hub 29 of the gear segment 28 is further provided with a counter bore forming a recess for the annular base flange 32 of a truncated cone or plug 33 which is formed preferably, although not necessarily, of Duralumin. The plug 33 is secured within the aforesaid hub 29 preferably by means of a force flt whereby said gear segment and said plug are permanently assembled as a unit.

in addition to the aforesaid splined hub 29, the index-coupling means includes a shouldered sleeve 34 having a series of external splines 35 on its reduced diametral portion 36 and a series of internal splines 31 on the inner periphery of its lowermost portion 38.

As shown, the sleeve 34 is disposed within the ring 36 which occupies an annular groove formed in the surface defining said bore II. The aforesaid sleeve 34 is further provided with an internal flange 46 adjacent the uppermost face thereof together with a pair of oppositely disposed, up- I standing lugs 4| Fig. 2, for a purpose hereinafter described.

A dished plate washer 43. a lock nut 44 carried by said washer. and a screw bolt 45 constitute means whereby the foregoing elements are maintained in cooperative relation. The washer 43 is provided with a pairof oppositely disposed tongues 46 struck out from the circular edge portion thereof, as clearly shown in Fig. 2, with the aforesaid lock nut 44, of the type known as an elastic stop nut," for example, staked, splined or otherwise secured in a central opening provided in said washer, whereby said washer and nut are permanently assembled as a unit. In order, as hereinafter described, for the washer 43 to be passed through the opening defined by the internal flange 40 of the sleeve 34 to the position illustrated in Fig. 1, the washer 43 is cut away at opposite sides thereof as at 41 whereby the necessary clearance is provided.

As shown in Figs. 1 and 2, the internal flange 40 of the sleeve 34 provides a support for the washer 43, oppositely disposed sections of the circular edge portion of the latter being disposed under the respective inwardly extending lugs 4| of the sleeve 34.

In order that the invention will be more clearly understood, the manner of assembling the foregoing elements will now be described, reference being had particularly to Fig. 8.

Assuming that the blade I3 is disposed in a horizontal position on a suitable assembly bench with its bare shank portion |2 in an overhanging position, the blade-retaining nut 23, without the lugs 23b and key 230, is passed over and well beyond the flanged root end of the shank l2. Thereupon, the seal 24 is manually stretched and, while so held, passed over the bare shank and positioned adjacent the nut 23. Next, the snap ring 220 is passed over the bare shank so as to be located adjacent the seal 24. The bearing I9 is now disposed on the shank I: by first passing the three one-piece outer ball races 22b over the root end of the shank end well beyond the said root end to a position adjacent the nut 23 and seal 24. The two. half-sections 20 and 2|, comprising the inner ball race of the bearing l9, are now disposed around the shank |2 with the lowermost faces of said half-sections 20 and 2| abutting the shoulder formed by the external flange l4. Thereupon, one set of half-sections constituting a ball cage 22, or a ball cage 22m, Fig. 6, are disposed around the assembled half-sections 20, 2|

of said bearing l9, at the lower end thereof. As soon as this has been done. one of the outer ball races 22b is moved along the shank l2 toward its root end until it is positioned around said halfsections of the ball cage 22 or the ball cage 2211.. In a similar manner, the remaining ball cages 22 or 2211 and the outer ball races 22b are assembled about said half-sections 20 and 2|.

After the uppermost or last outer ball race 221) has been moved downwardly along the shank i2 and over the sections 20 and 2|, the aforesaid snap ring 220 is moved along the shank and positioned in an annular groove provided therefor about the upper end portion of the said sections 20 and 2i whereby all three of the outer ball races 22b are held in stacked relation as shown. Thereafter, the bearing previously described, is positioned on the shouldered end portion of the external flange i4 and retained thereon by means of the aforesaid snap ring I. as will be understood.

In accordance with theinvention, the aforesaid assembling' operation may be performed by reason of the fact, (1) that the external diameter of the flange I4 is slightly less than the internal diameters of the nut 23 and ball races 22b, respectively, and (2) that the seal 24 is readily stretchable so that it may be passed over said flange I4.

The index-coupling elements hereinbefore described are now positioned in the shank bore II in the following manner, reference being had particularly to Fig. 1. The aforesaid splined sleeve 34 is slidably inserted in the shank bore II to bring the upper splines 35 thereon into meshed engagement with the splines l5. At this time, the snap ring 39 is sprung into the annular groove provided therefor in the shank bore 5 whereby the sleeve 34 is retained in its proper position.

When the washer 43 is to be disposed in operative position with respect to the aforesaid splined sleeve 34, the bolt 45 is threaded, to some extent, into the lock nut 44. Then, while manually holding the bolt 45, the washer '43 is tilted sufficiently to enable it to be passed through the opening defined by the internal flange '40 of the sleeve 34, this being possible by reason of the fact that opposite sides of the washer 43 have been cut away as previously described. After the washer 43 has been positioned above the flange 46, it is seated on the top surface thereof with its flat edges 41 opposite the respective sleeve lugs 4|. Finally, when the washer 43 is seated as described, the bolt 45 is threaded out of the lock nut 44, preparatory to attaching the blade-actuating gear segment 28 to the blade shank i2. In so doing,

the washer 43 moves with thebolt 45 until the washer tongues 46 engage the respective lugs 4| (which act as stops) in a position removed approximately degrees from that illustrated in Fig. 2. When engagement is thus effected between the tongues 46 and the respective lugs 4|, the bolt 45 may readily be removed from the washer 43. When the washer 43 is positioned as shown in Fig. 2, surfaces thereof are beneath the respective lugs 4| and the latter coact with these washer surfaces to positively retain it in seated position on the flange 46.

The splined hub 29 of the blade-actuating gear segment 28 is now slidably inserted in the shank bore I6 to bring the splines on said hub 29 into meshed engagement with theinternal splines of the sleeve 34. As previously described, the cone 33 is permanently associated with the gear segment 28 and'consequently it takes the position shown in Fig. 1. Thereupon, the bolt 45 is passed through the opening provided therefor in the cone 33 and threaded into the lock nut 44. Preliminarily, as the threading operation is initiated, the bolt 45 moves the washer 43 into the position shown in Fig. 2 wherein the washer tongues 46 engage the respective lugs 4| in a position the reverse of that described above. In this position, the washer 43 resists further turning movement and, therefore, the bolt 45 may be readily threaded thereinto to'positively secure the parts comprising the sleeve 43, the cone 33 and the gear segment 28 in the respective positions thereof shown in Fig. 1. I

For a description of another feature of the invention, reference is to be had to Fig. 11 in connection with blade design 836-1C2-X as manu- 11, the hereinbefore described gear segment 28 is shown as provided with a segment 28a terminating in spaced gear teeth 2812. As regards the load side, at pitch diameter, of the fifth gear tooth splines. Accordingly, for pitch-changing purposes, said gear segment 28 and the propeller 28b counting from the end of'the gear segment at the right, Fig. 11, a line Li is shown as extending therefrom through the center of said gear segment 28 and terminating at a point on the margin of the gear segment hub which is in line with the location at which a mark 49 is suitably formed on the vertical face 280 of said gear segment hub, Fig. 5.

Further in accordance with the invention, the splines 88 formed exteriorly on the hub 28 of said gear segment 28 are located in a predetermined manner with respect to the aforesaid gear tooth 28b and, hence, with respect to the mark 48. Thus, as shown in Fig. 11, the line Ll determines the location of the load side of one of the splines 88. With this as a basis, all of the splines 88 are spaced equidistantly with respect to each other.

In a conventional manner, as shown in Fig. 9, the blade hub of the above identified blade is shown in elevation, a transverse section at the 54-inch station being shown by thedot-and-dash lines and the chord line being indicated at L2. A line L8 forms anangle of 18 degrees with the line L2. From the center of the blade hub shown in Fig. 9, an arc is struck through an angle of 90 degrees from a vertical projection of the line L3 as indicated to obtain a point which, when connected with said blade hub center by a line L4, defines the location of a mark 58 which is suitably Iormed on the lower surface of the flange l4, Figs. 5 and 9.

When assemblies including the blade design of the type hereinbefore identified are to be produced, propeller blades l8, gear segments 28 and sleeves 84 are manufactured on a quantity basis. Within the limits imposed by manufacturing operations, all of the blades are duplicates and the same is true with respect to the gear segments and sleeves, respectively. Following the procedure hereinbefore described with respect to Figs. 9 and 11, the flange of each propeller blade has a mark 58 formed thereon and each gear segment hub has a mark 49 formed thereon. Therefore, as regards a group of the blades l8, the respective marks 58 thereon are a part of the duplicate character thereof and the same is true as regards the respective marks 49 of a group of the gear segments 28. Further, with respect to the gear segments 28 and following the procedure hereinbefore outlined, the sets of splines 88 are located in the same manner as regards the respective sets of gear teeth 28b.

Accordingly, during the assembling operation, any sleeve 84 may be selected and disposed in operative position interiorly of a blade shank as hereinbefore described. In so doing, the splines 85 are brought into meshing relation with the splines l5. Thereupon, any gear segment 28 may be selected at random and operatively positioned in the end of the blade shank. In so doing, the splines 88 are caused to mesh with the splines 21. However, this meshing position of the splines last named should be so selected that the marks 49 and 58 are alined as shown in Fig. 2. Finally, while the gear segment 281s held in the described position, the bolt 45 is passed through the opening provided therefor in the cone 38 and threaded into the lock nut 44 to hold the parts in assembled relation. In this manner, the gear segment 28 is secured to the blade shank by the two sets of blade are rotatively movable as a unit.

In' accordance with the invention, there are ninety-four of the splines l5 and the same number of the splines which coact therewith, the spIines of the respective sets being equidistantly spaced as will be understood. As regards the splines 88, however, there are ninety-five of these and the same number of the equally spaced splines 81 which coact therewith.

When the gear segment 28 is initially positioned in the end of the blade shank as described above, it is probable that there will be no meshing relation of the splines 88, 81 which would permit the marks 48, 58 to be exactly alined. Accordingly, assuming that the parts are assembled as shown in Fig. 1 wherein a certain relative position exists between the gear segment 28 and the sleeve 84, the bolt 45, gear segment 28 and snap ring 88 may be detached whereupon the sleeve 84 may be retracted to disengage the splines 85 from the splines l5, moved a distance of one of the spline teeth I5 or 85 in one direction and then returned to its splined relation with the splines l5. Thereupon, after the gear segment28 has been re-associated with the sleeve 84 in the same relative position as referred to above but, with the .splines 38, 81 disengaged, said gear segment 28, in a direction the reverse of that described above with respect to the sleeve 34, may be moved a distance of one of the spline teeth 81 and 38 and then returned to its splined relation with the splines 81.

Resulting from the operation just described, a new relative position is established between the gear segment 28 and the blade 18. With the form of the invention herein described, this new relative position is removed approximately of one degree from the original relative position between said gear segment 28 and the blade 18. This is true by reason of the fact that the minimum indexing increment of /25 of one degree is a function of the difference in angle between the ninety-five splines in the set of splines 88, 81 and the ninety-four splines in the set of splines I5, 85.

Assuming that the described one-spline relative movement was eifected between the gear segment 28 and the sleeve 34 in the proper respective directions, the'result may be'that the marks 49, 58 are brought into exact alinement. If not, the operation described may be repeated as often as necessary to secure the desired result.

It will be understood that the act of assembling the gear segment 28 with the sleeve 84 may cause the mark 49 to be on one side or the other of the mark 58. The direction of the initial onespline movement of the sleeve 84 will be dependent upon such location of said mark 49 with respect to the mark 58. Obviously, however, the subsequent one-spline movement of the gear segment 28 will be in a direction the reversed the direction of movement imparted to the sleeve 84.

Resulting from the assembling operation described above, blade assemblies are' produced which are duplicates within the limits imposed by manufacturing operations. on each blade assembly, the marks 48, 58 are in alinement and this means that the relation of the blade chord line L2 at the reference blade station to the fifth tooth load side of the gear segment 28 is the same within manufacturing tolerances for all the blade assemblies.

- The blade assemblies are now in condition to ill to the extent necessary to properly clamp the.

blade in position.

In connection with the foregoing, prior to the time that the nut 23 engages the uppermost raceway 22b, there is slight clearance, as a few thousandths of an inch, between the outer race i'ib and the lowermost raceway 22b. Accordingly, when the nut 23 initially engages the uppermost raceway 22b, force is transmitted to the half sections 20, 2| through the three sets of ball members 22a, this force passing from said half sections 20 and 2|, through the circular flanged section engaged by the bearing l1, thence through the inner race Ila and finally to the outer race lib by way of the ball members forming apart of said bearing l1. Thus, the pressure applied by the nut 23 to the bearing half sections 20, 2!

. preloads the bearings I1 and I9 but, with limited preload deflection, since the outer races 22b of the main hearing I 9 are brought to rest upon and are clamped on the exterior race Nb of the bearmg I! after a predetermined amount of deflection takes place in the bearings i1 and 9 to close the aforesaid gap which is initially left between the outer race 11b and the lowermost raceway 22b.

Accordingly, in the manner described, the blade is definitely located and properly secured in its socket. Side-play or "drooping of the blade with respect to the bore of the socket is minimized and the blade is prevented, from dropping into the hub l i should it become necessary to remove the power unit 2'? and its gear 26. It will further be observed that the bearings l1 and Ill take up a thrust load in opposite directions and that the main bearing l9 takes up the radial thrust exerted by the blade when in operation.

After the blade has been assembled in the socket ill as described above, the lugs 23b and key 230 are secured to the upper surface of the retaining nut 82 in accordance with conventional balancing procedure;

Assuming that the hereinbefore described hub M comprises three radial sockets 50, it will be understood that three of the duplicate blade assemblies of this invention will be disposed and retained in the respective sockets III in the manner hereinbefore described to thereby produce a to be true. However, in some cases, it becomes apparent in service that the balance is not satisfactory, this fault arising, probably, due to the lack of refined uniformity between apparently duplicate parts as imposed by manufacturing operations.

' unit. In a great majority of cases, this proves" Accordingly, when inservice. should the aerodynamic balance of the propeller prove unsatisfactory as stated, one of the propeller blades may be removed from the socket provided therefor. Thereupon in the same manner as previously described for bringing the marks 49, 50 into alinement, the gear segmentjn -and the sleeve 34 are moved in opposite directions to thereby obtain a new relation between said gear segment 28 and the other assembled parts. This is a relatively simple operation andit may be-performed, the results checked and-then performed again if necessary on one or more of the blades to obtain by trial-and-error procedure a satisfactory condition of aerodynamic balance of the propeller as a, unit. a

For purposes of explanation, a detailed description has been given concerning a detailed feature of the invention, namely, the two sets of splines. Obviously, the number of splines in the respective sets of splines may differ otherwise than by one spline and, further, there may be as many splines in the respective sets of-splines as may be desirbe interpreted sufficiently broadly to cover such toothed arrangements.

It shall also be understood that our invention, in its broad aspects, is not to be limited to the disclosed procedure for obtaining the location of the marks 49, 50 or equivalent. Obviously, these marks may be located otherwise than as described while still preserving the advantages of the invention. Further, as regards the procedure described, stations other than the 54-inch station may be used as desired.

The balance plug 23e serves as an anchorage for lead or the like whereby theweight of a blade may be increased or, alternatively, decreased for balancing purposes by removing small portions of previously added lead. When an operation of this character is to be efiected, the blade is removed from its socket whereupon the bolt 45, the gear segment 28 and washer 43 are disengaged from the assembly in the manner previously described. By way of the passage 40, then, access may be had to the plug 23c for the desired purpose. Thereafter, the parts just named are restored to their respective positions and, if the proper precautions have been observed, the restoration causes the marks 49, 50 to assume the relation taken thereby before disengagement of the parts was effected.

Furthermore, it is to be understood that while the present .invention has been described as applicable to a particulartype of hollow blade, it is equally applicable to other types of hollow blades I and also to solid blades wherein the shank portion may be provided with a bore for the reception of the index-coupling means herein shown and. described. v

As indicated in Fig. 2, the half-sections or raceway forming members 20, 2| detachably engage each other'at the two sets of surfaces 20a, 2la which are positioned diametrically'opposite each other. The half-sections 20 and 2|, then, are separate or separable from each other in directions perpendicular to a plane disposedat right angles to the longitudinal axis of the main bearll ing l9, this plane in the appended claims, being termed a plane extending transversely of the main bearing. It shall be understood that the half-sections 20, 2| may be so constructed that the sets of surfaces 200, 2la. defining the zones bets are designated as of the ball type. It shall be understood that this term is genericallyinclusive of true balls as well as anti-friction members of other shapes. 4 w

While the invention has been described with respect to a certain particular preferred example which gives satisfactory results, it will be under-. stood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, audit is intended therefore in the appended claims to cover all such changes and modifications.

What is claimed'as new and desired to be secured by Letters Patent, is: v

1. In combination, a propeller hub having a socket, a propeller blade having its shank journalled in said socket, said shank having a bore extending thereinto from its end, a balance plug secured in said bore, a driving member interiorly of said bore and secured in driving relation within and engaging said shank, said member having a passage through which access may be had to said balance plug, pitch-changing means engaging said driving member, and readily detachable means engaging said pitch changing means and driving member for holding said pitchchanging means in driving relation with respect to said member, said detachable means comprising a closure which, when inoperative position, closes said passage and, when detached, opens said passage.

2. In combination, a propeller hub having a socket, a propeller blade having a hollow shank joumalled in said socket, pitch changing means hub, a joint between the hollow shank of said having a portion projected within said shank,

means comprising a plurality of separate splined connections between said projected portions and shank for adjusting said propeller blade angularll with respect to said pitch changing means, the number of splines in one of said connections differing from the number of splines in another of said connections, and removable means engaging the internal wall of said shank and lying entirely within said shank for detachably securing said pitch changing means to said shank.

3. In combination, a propeller hub having a socket, a hollow propeller blade having its hollow shank journalled in said socket, means for moving said blade rotatably with respect to said socket to effect change in pitch thereof, means within said shank comprising an intermediate sleeve and a plurality of separate splined connections axially spaced with respect to the blade for connectin said first-named means to said shank, the numberv of splines in one of said connections differing from the number of splines in another of said connections, and removable means engaging the internal wall of said shank and lying entirely within said shank for detachably securing said moving means and sleeve means to said shank.

4. In a unitary propeller blade assembly for removal and attachment as a whole relative to a propeller blade and a pitch control gear element therefor, comprising a cylindrical wall in the shank hollow and a cylindrical boss on the element in fitting engagement with said wall, an annular row of n teeth formed within said shank, an annular row of n+m teeth formed on said boss. wherein n is a number of the order of 30 to and m is a number of the order of 2:1 to 1-5, a sleeve wholly within said shank and between said shank and boss having one annular row of n teeth engageable with said shank teeth and having another annular row of n+m teeth engageable with said boss teeth, whereby said shank and element may be adjusted relative to one another in a large plurality of different positions, removable means to secure said sleeve against axial displacement relative to said shank and element, and removable means to secure said element to said shank, both said removable securing means lying wholly within the confines of said shank and being removable from the base of said shank.

5. In a unitary propeller blade assembly for removal and attachment as a whole relative to a hub, a joint between the hollow shank of said propeller blade and a pitch control gear element therefor, comprising a cylindrical wall in the shank hollow and a cylindrical boss on the element in fitting engagement with said wall, an annular row of n teeth formed within said shank, an annular row of n+m teeth formed on said boss, wherein n is a number of the order of 30 to 100 and m is a number of the order of i1 to :5, a sleeve wholly within said shank and between said shank and boss having one annular row of n teeth engageable with said shank teeth and having another annular row of n+m teeth engageable with said boss teeth, whereby said shank and element may be adjusted relative to one another in a large plurality of diiferent positions, a removable abutment engageable with a portion of said shank wall to secure said sleeve in said shank and to hold the matching sleeve and shank teeth in engagement with one-another after said engagement is effected, and removable tension means securing said element to said sleeve, upon engagement of the matching boss and sleeve splines, whereby said sleeve and element are firmly secured to said shank.

JACK H. SHEETS. MAURICE E. CUSHMAN.

' REFERENCES GITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,951,321 Blanchard Mar. 13, 1934 2,032,255 Caldwell Feb. 25, 1936 2,113,478 Gobereau Apr. 5, 1938 2,135,190 Martin Nov. 1, 1938 2,208,602 Ruths July 23, 1940 2,307,101 Blanchard Jan. 5, 1943 2,308,488 Caldwell, et al Jan. 19, 1943 2,379,302 Hoover June 26, 1945 2,396,630 Anderson Mar. 19, 1946 FOREIGN PATENTS Number Country Date 546,054 Great Britain June 25, 1942 OTHER REFERENCES Controllable and Constant Speed Hamilton Standard Propellers, Service Manual -0, published Jan. 1, 1937. East Hartford, Conn. 

